The invention relates to a motor chain saw that comprises an internal combustion engine for driving a saw chain circulating about a guide bar. The crankshaft of the internal combustion engine is oriented transversely to a longitudinal axis of the motor chain saw and supports at a first end a drive pinion for the saw chain as well as at the second end a blower wheel of a cooling air blower. The cooling air stream that is sucked in by the cooling air blower is supplied transversely to the longitudinal axis of the motor chain saw for cooling the cylinder of the internal combustion engine, flows about the cylinder positioned between the drive pinion and the cooling air blower, and then is blown out through a housing opening at the opposite longitudinal side. The motor chain saw further has a handle that extends across the motor housing transversely to the longitudinal axis and a hand guard that is arranged between the handle and the front end of the guide bar and is secured with at least one leg in the area of the housing opening for the cooling air.
Modern internal combustion engines, in particular single-cylinder internal combustion engines, are operated with a lean mixture for environmental reasons; this may cause an increased operating temperature. In order to ensure a satisfactory cooling action, a corresponding volume stream of cooling air must flow through the motor housing. On the other hand, increased operating temperatures also cause a corresponding heating of attached parts, for example, the exhaust gas muffler.
It is therefore an object of the present intention to not only sufficiently cool the internal combustion engine with a cooling air stream but also to supply cooling air to an exhaust gas muffler that is attached to the cylinder.